This invention relates to track guided drilling equipment and, more particularly, to method and apparatus for moving track guided equipment to and from a track, such as the drilling track extending on the derrick of a subterranean drilling rig.
The top drive drilling system is a relatively recent innovation in rotary drilling. Rather than using a rotary table and kelly to rotate the drill string, as did prior subterranean drilling systems, the top drive drilling system uses a top drive which is connected to the top of the drill string and which may travel vertically with the drill string. The top drive is suspended from the traveling block and swivel and includes a carriage which connects the top drive to a drilling track which extends vertically along the derrick. The track and carriage both guide the top drive and resist the torque created by the top drive drilling motor during drilling.
The top drive is a heavy and expensive piece of equipment. It is required while drilling the well, but it is not needed in the hoisting system when the drill string and bit are being tripped in or out of the well. The top drive may be left in the hoisting system during tripping operations, although doing so causes unnecessary loading and wear on the top drive and the hoisting system. It is therefore advantageous to move the top drive from the hoisting system during tripping operations. There are also other reasons for removing the top drive from the drilling track, drill string, and hoisting system. For example, during service and maintenance of the top drive, it may be desirable to install a replacement top drive on the drilling track or to revert to conventional drilling equipment (rotary table, kelly, etc.).
When the top drive is removed from the drilling track, it is important to move it to a location where it does not interfere with the tripping or other operations taking place on the derrick floor. Normally the well center (the longitudinal axis of the well) is the hub of all activities on the derrick floor and it is desirable to keep the area around the well center as clear as possible. It is typical for a top drive drilling system to require an envelope of unobstructed space which extends along the longitudinal axis of the well center. For example, one top drive drilling system known to the inventors requires an envelope of unobstructed space which extends (as viewed from the front, i.e., the opposite side of well center from the drilling track) 2 feet forward of well center, 4 feet behind well center, and 3.5 feet left and right of well center, and which also extends 2 feet forward of well center and 2 feet behind well center from well center to the derrick on the right side of well center. The envelope circumscribing the well center is needed to allow the top drive and hoisting equipment to travel up and down over well center. The clear area extending to the right side of the derrick is needed for the service lines (mud line, air line, electrical power line, etc.) which travel up and down with the top drive (and also with the swivel of a conventional drilling rig). The area to the right of well center should also be kept clear when the casing stabbing board and air hoist lines are in this area. Normally the driller stands at a console on the derrick floor to the left of well center. The driller requires an unobstructed view extending from the console to well center at approximately ten feet above the racking platform in the derrick.
Apparatus for removing the top drive from the drilling track and hoisting system are known. For example, the assignee of the present invention in 1988 designed such a system. The assignee's prior system moved the top drive laterally relative to the axis of the well to a storage position. In the assignee's prior system, the top drive was lowered onto a guide track at the lower end of the drilling track; and the guide track and top drive were moved laterally relative to the axis of the well on a laterally extending track to an offset position in which the guide track was aligned with a storage track. The top drive was then lifted onto the storage track (which extended above the guide track). The storage track was then pivoted into a storage position where the top drive was supported in a position offset from the well axis. After the top drive was lifted onto the storage track, the guide track could be moved back into alignment with the drilling track and used to guide the traveling block dolly and other track guided equipment. This system had several shortcomings, for example, it required the use of a support line to assist in supporting the top drive on the storage tracks; required the connection of a raising sling between the traveling block and top drive to lift the top drive onto the storage track, followed by the disconnection of the raising sling from the traveling block; and the laterally extending track was immovable and obstructed the clear space or envelope needed on the right side of well center.
U.S. Pat. No. 3,835,940 (Winter, Jr.) discloses a drilling head connected to a carriage by a pivot pin so that the drilling head may be swung about a vertical axis to a position laterally of the drilling axis. A reversible hydraulic ram serves to move the drilling head between lateral positions. Movable latches, operated by a ram, are provided to lock the drilling head to the carriage during the drilling operation and for releasing same for movement of the drilling head away from the drilling position. A shortcoming of the Winter apparatus is that the distance the drilling head may be offset is limited to the length of its radius from the pivot point and in many cases this may be insufficient because it does not move the drilling head out of the clear space or envelope needed for the traveling block and other equipment which it may be desirable to use while the drilling head is removed from the drilling track.
U.S. Pat. Nos. 4,421,179 and 4,437,524 (Boyadjieff) disclose track sections and their connected parts, including the carriages and drilling unit, which are swung about a vertical axis to a position offset from the drilling axis. In the Boyadjieff apparatus, the distance the drilling unit may be offset is limited to the distance between the drilling unit and its pivot point. This may be insufficient for the same reasons as given for the apparatus of U.S. Pat. No. 3,835,940.
U.S. Pat. No. 5,038,87 (Dinsdale) discloses apparatus for laterally moving a direct drive drilling unit from the drilling or working rails to an offset position relative to the axis of a well. In a first embodiment, a pivotable frame carries a first pair of rails, which are aligned with fixed upper rails during drilling, and a second pair of rails used to support the drilling unit when it is to be offset. When the drilling unit or power swivel is to be removed from the upper rails and drilling system, the second pair of rails, or skids, are rotated into alignment with the upper rails and the power swivel is lowered by drawworks until the lowermost roller contacts stops on the skids. The frame is then rotated counterclockwise on a curved track until the first pair of lower rails is aligned with upper rails. Lock pins are used to engage the first pair of lower rails to the upper rails. Lock pins are also used to engage the frame to the structural braces to prevent rotation of the frame. In a second embodiment, the first pair of lower rails and second pair of lower rails are connected to a frame having an upper horizontal beam and a lower horizontal beam. When it is desired to position the power swivel in an offset or inactive position, lock pins are removed from rail splices and lock pins are removed from holes and flanges of the lower track and from the holes and flanges welded to the back side of rails. The frame is then slid from right to left relative to the well axis until it contacts a blocking top surface. This coincides with the second pair of lower rails, or skids, being aligned with the upper rails. The power swivel is then lowered until it is supported by stops. After disconnecting the power swivel from the traveling block, frame may be slid from left to right and returned to the position in which the first pair of lower rails is aligned with the upper rails. In the first embodiment of Dinsdale, the pivotable structure behind the rails obstructs the are behind the track and moves through the area behind the track which both obstructs the vision of the workers and prevents the use of the area behind the track for service lines, such as the fastline of the drawworks. Also, the distance the power swivel may be offset is limited to the radial distance from its pivot point, which may be insufficient to clear the unobstructed space or envelope needed around well center. In the second embodiment of Dinsdale, the frame used for lateral motion of the top drive extends immovably to the right of the drilling tracks and obstructs the space needed to the right of well center for such equipment as the service lines, the casing stabbing board, and the air hoist.
Despite the prior attempts to provide an apparatus for removing a top drive from the drilling track and hoisting system, a need exists for an apparatus for moving track guided equipment to and from a track, such as the drilling track of a subterranean drilling rig, which will both remove the top drive from the drilling track and which will locate the removed top drive at a position which does not obstruct the space needed around well center and on the derrick floor for activities which take place while the top drive is removed. The patents referenced in this application illustrate the long-felt need for an apparatus having these properties. There is also a commercial need for such an apparatus which is relatively inexpensive and easy to use.